After moving all mailboxes from a mailbox database to other mailbox databases (both in Exchange 2016), including archive and arbitration mailboxes the mailbox database still cannot be deleted. Trying to remove the mailbox database still generates the following error message:
This mailbox database contains one or more mailboxes, mailbox plans, archive mailboxes, public folder mailboxes or arbitration mailboxes, Audit mailboxes. To get a list of all mailboxes in this database, run the command Get-Mailbox -Database <Database ID>. To get a list of all mailbox plans in this database, run the command Get-MailboxPlan.
Get-Mailbox -Arbitration or Get-Mailbox -Archive doesn’t return anything.
Exchange 2016 introduced a new type of mailbox, the auditlog mailbox. This can be returned by the Get-Mailbox -Auditlog command:
Move this auditlog mailbox to another mailbox database and the old mailbox is now fully empty and can be deleted.
Jaap Wesselius 
If I am not mistaken, this only applies to Exchange 2016 servers. Because Exchange 2013 and older do not have this type of mailbox, this specific reference would not apply if you are decommissioning those server versions after transitioning to Exchange 2016.
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Hi Todd, thanks for the feedback. You’re right, this is a typical 2016 issue. Made a small change in the article point to Exchange 2016, thanks
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What’s funny is that if you look at the -AuditLog switch from the Get-Mailbox help, it states: “This parameter is reserved for internal Microsoft use.”
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That’s funny, I never noticed that 🙂
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I have tried pretty much everything and I still can not remove a database. It has no arbitration, archive, public folder, or audit log mailboxes. It had one mailbox and it has been removed. It is EXTREMELY frustrating as I want to remove the server without having to resort to ASDIEdit. I am sure this is a bug in 2016 CU5. This is a brand new install.
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I agree, it’s extremely frustrating to end up in a situation like this, especially when it’s a brand new install. But I’m afraid the only thing you can do is use tools lik ADSIEdit or LDP to find the hidden links.
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